The present invention relates, in general, to electronics, and more particularly, to methods of forming power supply systems and structures.
In the past, the electronics industry utilized various implementations of power supply systems to provide power to a load. Typically these implementations were classified either as linear power supply systems or non-linear power supply systems. Linear systems typically utilized an error amplifier to sense an output voltage and control a pass transistor to achieve a desired output voltage. One example of a linear system is disclosed in U.S. Pat. No. 4,803,612 issued to Timothy J. Skovmand on Feb. 7, 1998, which is hereby incorporated herein by reference. Such linear systems generally provide a faster response to changes in the load voltage and have very low output noise. However, such linear systems typically were not very efficient. Non-linear systems typically include a switching control element that periodically enables and disables a pass transistor to provide power to the load, sometimes referred to as varying the duty cycle of the pass transistor. One example of such a non-linear regulator is disclosed in U.S. Pat. No. 5,617,016 issued to Maria R. Borgi et al on Apr. 1, 1997, which is hereby incorporated herein by reference. Such non-linear regulators were more efficient than linear regulators but provided a much slower response time to changes in the load voltage.
In some applications such as battery operated applications and particularly for cell-phone applications, it is important to have efficient operation and fast response time in order to provide maximum battery life. Accordingly it is desirable to have a power supply control system that has efficient operation and a fast response time.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor.